1. Field of the Invention
This invention relates to an exposure calculation device for cameras.
2. Related Background Art
The present applicant has proposed an exposure calculation device for cameras, in which focus detection is carried out for a principal object in a photographic frame by a focus detecting device; the result of the focus detection is utilized to obtain the respective defocus amounts in the different photometric areas of a divisional photometer device, effecting weighting on the respective photometry outputs of the photometric areas; whereby a correct exposure for the principal object is calculated (see Japanese Patent Application No. 1-231041).
The above exposure calculation device, however, has the following problem: In the case of a sharply backlighted principal object, the photometry output is excessively low in that portion of the photoelectric transfer element array of the focus detecting device which corresponds to the principal object, so that defocus amount detection cannot be effected, making it impossible to calculate a correct exposure for the principal object.
If, on the other hand, the principal object is being spotlighted against a dark background, i.e., if it is in a sharply front-lighted condition, the photometry output is at an excessively high level in that portion of the photoelectric transfer element array of the focus detecting device which corresponds to the principal object, which means that the defocus amount of that portion cannot be detected, thus involving the same problem as in the above case.